Eating with a non-Jew
The Quote
If you eat with a Goy, it’s the same as eating with a dog
– Tosafos, Yevamos 84b
The Reality
The quote is entirely made up.
First of all, Tosafos is not the Talmud, it’s a commentary on the Talmud made by rabbis living in Europe in the 11-15th centuries.
Secondly, and more importantly, this quote does not appear in any of the Tosafos on Yevamos 84b. Neither eating with non-Jews nor dogs are discussed there at all.
Summary:
The “quote” is entirely made up. It does not exist.